1.1 Field of the Invention
The present invention relates generally to the detection of cervical cancer, and more particularly, to a method and portable apparatus for the visual examination and grading of cervical epithelium by means of a hand-held colposcopy assembly capable of producing a digital image of the cervix.
1.2 Problems in the Art
1.2.1 General Setting of the Invention
Two methods are used for early detection of cervical cancer and precancer: cytology and colposcopy. Cytology is a screening method that is practical and economical and colposcopy is a diagnostic method directed to the clinical diagnosis of patients with abnormal cytology.
1.2.2 Conventional Methods and Systems. PA1 1.2.3 Conventional Portable Colposcopy Assemblies PA1 1.2.4 Conventional Computerized Colposcopy
Over the last fifty years, Papanicolaou Smear ("Pap Smear") has become the principal cytology screening method and the cornerstone of efforts to reduce cervical cancer mortality. Pap Smear screening is effective in identifying the later stages of cervical cancer. Current estimates are that 60-70 million Pap Smears are done in the U.S. each year. Pap Smear screening has, thus, become the standard screening method for the detection of cervical cancer.
When conducting Pap Smear screenings, the gynecologist collects exfoliated cells from the surface of the cervix and places them on slides that are sent to cytologists for further examination. Cytologists then review the cells placed on the slides and look for abnormal cells. If abnormal cells are found, the Pap Smear is considered to be positive. If no abnormal cells are found, the Pap Smear is considered to be negative. In some cases, the Pap Smear slides cannot be properly evaluated by the cytologist because of technical problems associated with the Pap Smear collection process such as inadequate cell count, improper slide fixation, etc.
In the early stages of cervical disease, abnormal cell exfoliation is slow and most abnormal cells are located below the surface or are trapped by a keratin barrier covering the cervical surface. In these circumstances, the Pap Smear screening process is a relatively insensitive indicator of cervical health due to inaccessibility of abnormal cells that are otherwise indicators of cancerous or pre-cancerous tissue. HPV virus is the most common cause of keratin barriers hindering exfoliation and a significant portion of the U.S. population is known to harbor the HPV virus. This complicates the challenge of abnormal cell collection in the Pap Smear procedure.
Because of a variety of problems associated with Pap Smear screening, it is well known that the Pap Smear procedure has a high false negative and a low but statistically significant false positive rate. Studies indicate that Pap Smear screenings will fail to detect from 50%-80% of low grade cancerous lesions and even 15%-30% of high grade cancerous lesions. Repeating the Pap screening on a regular basis helps to improve on this failure to detect, but still misses an unacceptable level of diseased patients. 40% of cervical cancers occur in women who have had reasonable Pap screening. Nevertheless, in spite of its cancer detection shortcomings, Pap Smear screening is generally recognized as a practical and economical procedure for the early detection of cervical cancer.
While the Pap Smear process is designed for initial screening, colposcopy and related procedures are generally used to confirm Pap Smear abnormalities and to grade cancerous lesions. Conventional colposcopy is a subjective visual assessment of the cervix and the quality of this assessment depends greatly on the expertise of the practitioner. Since its introduction in 1925, colposcopy has acquired wide recognition as the standard follow-up clinical procedure for patients identified by Pap Smear screening as having possible cervical abnormalities. It is generally recognized that colposcopy is highly effective in evaluating patients with abnormal Pap Smears and has therefore become the standard of medical care in the Western world for this circumstance. It is estimated that approximately 4 million colposcopy examinations are currently performed in the U.S. each year.
The simultaneous use of cytology and colposcopy is potentially the most effective screening method for cervical cancer detection. The use of present-day colposcopes, however, requires special expertise, is time consuming and costly, and thus, effectively precludes its use as a standard screening method. The typical colposcope weighs between 35 and 80 pounds necessitating that it be movable (e.g., through wheels) or be permanently placed in a room. It requires time to set up as the binocular lens system and base must be positioned and oriented to aim at the exposed uterine cervix. Once oriented, the cervix must be actively visualized through the optics to insure the cervical tissue is in focus.
Although use of a colposcope as a diagnostic method for cancer detection is potentially highly effective, colposcopy is not widely used because of the special expertise required for use and interpretation of visual information collected.
Attempts have been made to overcome the problems referenced above as associated with the use of colposcopy as a screening method. For instance, U.S. Pat. No. 4,300,570 to Stafl and U.S. Pat. No. 4,519,684 to Francis, et al. disclose a diagnostic screening method using a portable photocolposcope operable to create photographs of cervical tissue. The photocolposcope includes a single lens reflex camera equipped with an extender and a telelens which is mounted on the extender. The photocolposcope is operable to create photographs that may be converted into slide photographs of the cervix. The slide photographs are then projected onto a screen for visual evaluation by individuals having an expertise in cervical cancer screening and diagnosis. Because photographs are produced by the photocolposcope (i.e., a photograph capable of taking photographs) and its associated method, many of the limitations associated with conventional colposcopy are avoided. More particularly, the photocolposcope and method may be effectively used by persons lacking the extensive skill and training otherwise required for proper operation of conventional colposcopes and data interpretation.
Although an improvement, the photocolposcope and its associated method, disclosed in the '570 and '684 patents, suffer from a number of other problems. The effectiveness of a colposcopic photocolposcopic evaluation is highly dependant upon the image clarity since cancer diagnosis is dependant upon effective examination of tissue color, surface texture (i.e., roughness, smoothness), tissue borders (i.e., borderline between the lesion and the normal epithelium) and vascularity (i.e., capillary pattern, intercapillary density and distance). At the time a colpophotograph is created, the operator does not receive instant feedback and thus cannot be aware of problems resulting from any number of clinical or technical defects inherent in use of a photocolposcope. For example, an appreciable percentage of photographs created by photocolposcopes are defective for clinical reasons because of mucus or foreign objects obscuring the field of vision, or because a lesion may not fully be included in the field and for technical reasons because of the presence of undesirable reflective glare, inadvertent over or under exposures, and processing problems typically associated with conventional photography (including chemical and paper quality and age degradations). Yet further, the delay associated with the photocolposcopic processing method implies that: (i) the attending physician can never "see and treat" the patient; and (ii) subsequent patient examinations are often required when developed colpophotograph are later found to contain defects. Finally, although photographs are sent to experts for review and interpretation, subjective analysis of the colpophotographs still occurs and experts reviewing the photographs have only limited access to source information.
The recent emergence of computer-aided colposcopy creates a potential for the enhancement of colposcopic assessments. Computer-aided colposcopy provides for expanded utility in digital colposcopic photography and videography, and in the management of information generated by the colposcopic examination, including computer-aided processing and enhancement of colposcopic-generated images. Computer-aided colposcopes are able to analyze images instantaneously and, under the guidance of an experienced operator suggest an objective diagnosis with a degree of accuracy beyond what experienced colposcopic operators obtained using traditional methods. Computer-aided colposcopy also sets up a platform that will facilitate the emergence and development of "telemedicine" by permitting the communication of diagnostic digital image information across telecommunication networks. See, for example, Cristoforoni, M.D., Gerbaldo, M.D., Perino, M.D., Piccoli, M.D., and Capitanio, M.D., Computerized Colposcopy: Results of a Piolot Study and Analysis of Its Clinical Relevance, Obstetrics & Gynecology, Vol. 85, No. 6, (June 1995); Contini, M.D., Zobbi, M.D., Pasquinucci, M.D., Colposcopy and Computer Graphic: A New Method?, AM J Obstet Gynecol (1989); Shafi, Dunn, Chenoy, Buxton, Williams, Luesley, Digital Imaging Colposcopy, Image Analysis and Quantification of the Colposcopic Image, British Journal of Obestrics and Gynecology, Vol. 101, pp. 234-238, (March 1994); Mikhail, M.D., Merkatz, M.D., and Romney, M.D., Clinical Usefulness of Computerized Colposcopy: Image Analysis and Conservative Management of Mild Dysplasia, Obstetrics & Gynecology, Vol. 80, No. 1 (July 1992).
Computerized colposcopy, while capable of generating, storing and manipulating image data for the production of high-quality images, is likewise suffering certain technical difficulties. Equipment size, cost, and complexity considerations create disincentives against the use of computerized colposcopy. Further, like film photography-aided colposcopy, a difficulty encountered with computer assisted digital colposcopy is reflective glare resulting from the reflection of colposcopic illumination from wet cervical tissue and its associated derogatory effect on visualized and digitally captured image quality. Technical difficulties resulting from reflective glare have been reported in the literature as responsible for significant percentages of computer-aided colposcopic captured images rendered unreadable.
A two-fold need, therefore, exists in the area of cervical-cancer detection. A simple, low-cost, portable, hand-held colposcope and colposcopic technique are needed for use in conjunction with or in place of the conventional Pap Smear procedure to improve the overall statistical accuracy of screening efforts. In addition, traditional colposcopy should be easier to perform by reducing the subjectivity of the examination and should further be capable of producing archivable images that are devoid of technical flaws and inadequacies and are readily available for subsequent exams.